This invention relates generally to monitoring network transmission.
The needs for coordinated monitoring of network transmission can be best described by reference to the following particular application.
Worldwide deregulation and packet-switched technology have brought dramatic changes to the telecommunications industry. Voice communication over packet-switched networks, such as, the Internet, is now in demand. Voice Over the Internet technology is now available which integrates a public switched telephone network (PSTN) and the Internet. Voice over the Internet technology is also referred to as, Voice over Internet Protocol (VoIP), Voice over IP (VOIP) uses the Internet Protocol (IP) to transmit voice as packets over a network using the Internet Protocol. So VoIP can be achieved on any data network that uses the Internet Protocol, like Internet, Intranets and Local Area Networks (LAN). In order to transmit a phone call over a data network that uses the Internet Protocol, the voice signal has to be digitized, (in some cases compressed) and converted to IP packets and then transmitted over the IP network. In addition to the voice data (sometimes called media), signaling data is also sent. Signaling protocols are used to initiate and end calls and carry information required to locate users. Internet telephony is desirable since the cost involved is very low.
A PSTN can include transmission components (links), switching components (nodes), and billing facilities. The Internet can be any network or combination of networks that support packet-switching. Such a network can include, but is not limited to, a network supporting the Internet Protocol (IP) and related protocols.
VoIP systems allow a call originating from a PSTN to be carried over the Internet. However, VoIP calls can originate from phones, sometimes referred to as IP phones, not connected to a PSTN. In both instances, voice traffic can be carried over the Internet bypassing more expensive long-distance carriers.
A VoIP system should perform to the level of service obtained from a PSTN based system. Among the key factors in obtaining the substantially the same level of service is the Quality of voice. The Quality of voice is influenced by the choice of codec, echo control, packet loss, delay, delay variations (jitter) and the design of the network. As IP was designed for carrying data, it does not provide real time guarantees but only provides best effort service. For voice communications over IP to become acceptable to the users, the delay needs to be less than a threshold value.
To reduce or avoid noise and distortion in a VoIP network (or any network for that matter), it is important to be able to characterize it or measure it in some way.
For VoIP, specialized testing methods are often used.
In VoIP network testing significant information can be obtained by passive monitoring. Passive monitoring is a testing method in which the test device or process “listens” to some aspect of the voice traffic to gather statistics and perform various types of analysis. Passive monitoring is non-intrusive and does not affect voice traffic or network behavior. It is often used in digital environments in which information, which is encapsulated in frames, cells, or packets, can be used to alert test personnel of a problem, or can be analyzed later to determine problem causes and identify traffic trends. The results of the passive testing can be used to obtain predictive MOS (Mean Opinion Score) results.
In one embodiment of passive monitoring, individual monitoring devices report testing results to a central location or server. This reporting identifies the status or “worst case” condition observed at one or more points in the network. It is likely that points in the network are reporting a wide range of abnormal (possible “worst case”) conditions. Therefore, it is difficult to diagnose where in the network the “worst case” condition exists or the nature of the root cause of the error (“worst case”) condition.
Hence, there is a need for coordinating the collection of information about an individual call across multiple network segments in order to provide end-to-end analysis.
In other data networks, there is also a need for coordinating the collection of information about an individual network transmission across multiple network segments in order to provide end-to-end analysis.